Project Summary This application for a K23 mentored career development award integrates structured career mentorship and in- depth research training with a detailed research plan is designed to foster the career as an independent investigator of Jonathan S Litt, MD, MPH, ScD is a neonatologist at Beth Israel Deaconess Medical Center and Instructor of Pediatrics at Harvard Medical School. At the completion of the award period, Dr. Litt achieved a high level of methodological expertise in advanced data collection and analytic techniques and their application to the intersecting trajectories of chronic respiratory ailments and developmental comorbidities and developing interventions aimed at improving functional outcomes in high-risk populations. Dr. Litt's career development plan involves training in 1) using large data sets to develop and test hypotheses, 2) managing patient-oriented research with large cohorts, and 3) using advanced methods for longitudinal trajectory analysis. The overarching scientific aim of this K23 award proposal is to elucidate the relationship between the development of chronic respiratory disease (wheezing, asthma) and behavioral problems in a clinical sample of high-risk preterm (PT) infants with chronic lung disease (CLD) and a large population-based birth cohort. Understanding this relationship will help inform the content and timing of targeted interventions to decrease functional morbidities and prevent disabilities, particularly in high-risk populations. Aim 1 is to assess the longitudinal relationship between wheezing-related respiratory status and behavior problems in healthy term-born children. Aim 2 is to describe the emergence and trajectory of respiratory symptoms in among PT infants with CLD. The findings of the proposed studies will fill key gaps in understanding of how physical health and behavioral functioning interact over time and inform the timing, suggest content of interventions for reducing morbidities associated with chronic disease in childhood and provide the basis for an R01 grant. Following the K23 award period, Dr. Litt will be well-positioned to apply for further federal funding as an independent investigator to develop test evidence-based interventions.